Draft producing apparatus



April 1946- s KNEASS, JR 2,397,870

DRAFT PRODUCING APPARATUS Filed Feb. 24, 1943 STRICKLAND KNEAss, JR.

Patented Apr. 2, 1946 UNITED STATES PATENT OFFICE DRAFT PRODUCING APPARATUS Strickland Kneass, In, Boylston, Mass., assignor to Morgan Construction Company, Worcester, Mass, a corporation of Massachusetts Application February 24, 1943, Serial No. 476,946

2 Claims.

. withdrawal and discharge of hot gases by means of a powerful air jet associated with a suitably constructed stack, the gases being entrained by the air and carried along therewith through the stack. Cold air is employed, and the temperature of the mixed air and gases is ordinarily low enough to avoid damage to the stack. However, if the gases are unusually hot,'the temperature of the mixture will be too high for an ordinar steel stack to withstand, and it has been considered necessary in such cases to construct the stack of very expensive heat-resisting materials, resulting in prohibitive costs.

It is accordingly one object of the invention to provide a draft producing apparatus which can be constructed of comparatively inexpensive materials and Which will be capable of handling gases at unusually high temperatures.

It is a further object of the invention to provide an ejector of the air jet type which will automatically maintain a predetermined draft for the withdrawal of hot gases from a furnace or the like and at the same tim prevent the temperature of the mixed air and gases from exceeding a safe value.

With these and other objects in view, as will be apparent to those skilled in the art, the invention resides in the combination of parts set forth in the specification and covered by the claims appended hereto.

Referring to the drawing illustrating on embodiment of the invention and in which like reference numerals indicate like parts, the single figure is a vertical section through a draft producing apparatus adapted to handle unusually hot gases.

The embodiment illustrated comprises a vertical passage It for the upward flow of the hot gaseous products of combustion from a furnace (not shown). At its upper end this passage I converges to direct the ases into the lower end of an upright metal stack I I which diverges gradually in the upward direction. The passage It is provided with a lining I2 of a suitable heat-resisting material such as fire-brick or the like. A nozzle I4 is mounted within the passage In in position to discharge air upwardly into the lower end of the stack I I, thereby entraining the gases and discharging them from the upper end of the stack to the atmosphere.

tion air is supplied to the nozzle I4 through a duct I5 by means of a suitable fan I6.

The air from the nozzle I4 will mix with the gases and cool them considerably. However if the gases are unusually hot, the temperature of the mixture will be too high for the stack I I to withstand safely unless it is made of very expensive material, as otherwise there will .be danger of overheating and oxidizing the stack. This danger is avoided in accordance with the present invention by admitting additional'air int the lower end of the stack, preferably directly from the atmosphere, in quantities sufficient to cool the gaseous mixture to a safe temperature. For this purpose the lower end of the stack is provided with a series of circumferentiallyspaced holes I8 which are surrounded by an annular chamber or manifold I9. This chamber I9 is connected with the atmosphere by a short duct 20. Since the pressure within the lower portion of the stack is subatmospheric when the apparatus is in operation, a flow of air will be induced through the duct 20 and chamber I9, and thence inwardly through the openings 18 into the stack to cool the gases there-- in.

The admission of this cooling air through the openings I8 is preferably controlled automatically to prevent the temperature of the mixture within the stack from exceeding a safe value. A illustrated, the duct 20 is provided with a damper 22 having an operating arm 23 connected to a hydraulic motor 24. The opposite ends of this motor are connected by means of two pipes 26 and 21 to an automatic regulator 28. "This regulator comprises a pivotally mounted nozzle 30 to which fluid 7 under pressure is supplied from a suitable source through a tube 3|, the nozzle having its discharge end located adjacent the ends of the pipes 26 and 21. The nozzle is arranged to be moved about its pivot by means of a corrugated metal bellows 33 which is connected by a capillary tube 34 to a temperature responsive device 35 located within the stack II. This device is in the form of a hollow bulb containing a suitable liquid or gas which will expand upon increase in temperature and thereby force the bellows 33 to expand and move the nozzle 39 downwardly. The nozzle will thereupon deliver fluid into the pipe 26, causing the motor 24 to open the damper 22 and admit cooling air into the stack. It will be understood that while fluid is entering the pipe 26 from the nozzle, fluid from the pipe 21 will be exhausted into the interior of the regulator casing, which is maintained at atmospheric pressure by a suit- I This so-called "ejecas able vent or drain (not shown).

Changes in the rate of air admission to the stack through the openings [8 will tend to vary the draft in the passage [0, whereas a steady and uniform draft is ordinarily desirable. Accordingly means is provided to regulate this draft automatically. For this purpose the duct I5 is provided with a damper 31 having an operating arm 38 connected to a hydraulic motor 39. The opposite ends of this motor are connected by means of two pipes 4| and 42 to an automatic regulator 43. This regulator comprises a pivotally mounted nozzle 45 to which fluid under pressure is supplied from a suitable source through atube 46, the nozzle having its discharge end located adjacent the ends of the pipes 4| and 42. nozzle is arranged to be moved about its pivot by a flexible diaphragm 48 and an adjustable tension spring 49, the diaphragm being subjected to the sub-atmospheric pressure within the passage [0 through a pipe 50. The casing of the regulator 4H ma ntai ed at tm spheri e u b he 0 9 h t he 91; ases i l e s a e f ithe ii ac a Fe 61 y the air a d d ch ed .ki thirl smr a u e o r. 7; liters: approach s y 7. 9 13 or wheisr rim a mum value is: iprt meta wa l f the 2%??? 2 will respond automatiis dam er. 2? o pen and admit a rein the atmosphere int the stack through i 9 PES H Q SJB t9 92M1 9 as th n, The r g wil bs pesnsdonly the amou t required Q Y are he t mpe ature, o the mixture below the i lgfi, 29m headmission of this, coolin air w me th draftinthepassageH1, but he sli htest reducti n n this rait will be trans? mitted through the pipe 58 to the regulator 4.3. Th s-in will gperi the damper '31. and increase The 115 (a slib-a mils ht c pri iireor d a tthe air flow to the nozzle just enough to restore the desired draft. Thus both the dampers 22 and 37 will be held automatically as nearly closed as possible while maintaining the necessary draft in the passage l0 and keeping the temperature of the gases in the stack H below the danger point. Because of this automatic protection it is feasible to FQQ P QPHF (Stack f QWWWE QY i sive material even though yer}; hot furnace gases are to be'hand-led.

Having thus described my invention, what I claim as new and desire to secure by Letters Pat n 1. Apparatus for the drafting of hot gases com- 7 prisin-ga conduit for the flow of the gases to the atmosphere, means to discharge airunder pressure into the conduit to entrain the gases and -;f1,.0w thereof in the direction desired, means to control the rate of the said air discharge in accordance with the draft in the conduit, means i dmit add ional ai W9 heandhi t9 9 e seaweed prevent ve he ting 9f he emimsans o on r l the rats o ad on of th said additional air in accordance w th the terns Ps-r ir f he m ss d a r and ga es in the conduit.

2- Appa atus i9! thsqra tins of hot gase .0 1. ir sias ras a e i r as s oprish stack ilqmmim cat n a s l we end on the pas a e and open t its 5. i to t, atmosphere, a noz l to Mi cha, so pwa d y into th lower Portion o the s ack r the a e t ained and carried urwardlr-throughtne stack, a v, iiwt leadin to he :a tan tosu-p y air to the Q JFJt, a s am sr. the cluct, an automatic Wel to a aneed to actuate the dampe a s ri ance Wit the dlTJ-tin the passa th a having openings in its lower portion for the ad: ission of air directly from the atmosphere, a dam er to control the airflow thr h the ope ns Land an a tomatic regulator arranged to actuate the lastementigneddamper accordance with the temperature of the mixed-air andgases Within-thestack.

STRIGKLAND KNEASS, JR. 

